The present invention relates to a spring case device for a music box.
It has been customary practice to make spring cases for music boxes by deep-drawing thin sheets of steel. Another known type of spring case is molded of an alloy of zinc by die casting.
The spring case of the music box serves to rotatably hold a first shaft and a drum body and also to secure one end of a spring while preventing the spring from being unwound. Accordingly, the spring case is required to be precisely machined and mechanically strong, and in addition should meet requirements as to appearance, such as color and design.
With the spring cases of deep-drawn thin steel sheets, there are certain limitations as to shape, and those of complicated configurations are difficult to design. Such spring cases have therefore prevented a reduction in the number of parts and the cost of music boxes.
The spring cases fabricated by way of die casting can be molded in complex shapes, but result in an increase in the cost of material used. It is known that the overall weight of a finished music box should be balanced about a vibrator plate. Since, however, the die castings are heavy, the required weight balance is not obtained and the quality of sound generated by the music box is reduced.
The above difficulties can be eliminated by fabricating spring cases of synthetic resin. Spring cases of synthetic resin, however, are disadvantageous in that if they are made thinner for a reduction in size, the mechanical strength thereof becomes smaller.